1. Field of the Invention
The present invention relates to a bearing unit used for a rotation supporting portion of, for example, a gear incorporated into a transmission. The present invention also relates to an assembling method of the bearing unit.
2. Description of the Related Art
As for this type bearing unit, as shown in FIG. 12, there is known a bearing unit includes a rolling bearing 4 having a plurality of rolling elements 3 disposed between an inner ring 1 and an outer ring 2 as shown in FIG. 12, and a retainer plate 5 which contacts with an axial end face of the outer ring 2 of the rolling bearing 4 to fix the rolling bearing 4 to a housing H. (For example, see Japanese Patent Unexamined Publication No. JP-A-2004-028123.)
It is demanded to downsize automobiles and at the same time it is demanded to downsize transmissions. In order to meet these demands, there is provided a structure shown in FIG. 13 in which a small diameter step portion 6 is formed in an end axial portion of an outer circumferential face of an outer ring 2 of a rolling bearing 4 and a retainer plate 7 is engaged and fixed to the small diameter step portion 6. (For example, see German Patent Publication DE 102004031830.
In this bearing unit, after the retainer plate 7 has been inserted from the outside into the small diameter step portion 6 of the outer ring 2, a plurality of portions in the circumferential direction of a circumferential edge of an inner circumferential portion of the retainer plate 7 are pressed and deformed in the axial direction. Due to this pressing and deforming work, a plurality of engagement pawls 8, which protrude inside in a radial direction, are formed in a plurality of portions in the circumferential direction in the inner circumferential portion of the retainer plate 7 inserted into the small diameter step portion 6. These engagement pawls 8 are engaged with the engagement groove 9 formed on an outer circumferential face of the small diameter step portion 6.
Compared with the structure in which the retainer plate 5 is contacted with an axial end face of the outer ring 2 shown in FIG. 12, this bearing unit is advantageous in that a size in the axial direction can be reduced and a transmission can be downsized.
However, in the DE102004031830, after the retainer plate 7 has been inserted from the outside, a plurality of portions in the circumferential direction of the circumferential edge of the inner circumferential portion are pressed in the axial direction, so that the engagement pawls 8 engaging with the engagement groove 9 of the outer ring 2 are formed in the inner circumferential portion of the retainer plate 7. Accordingly, it is difficult to check whether or not the engagement pawls 8 are properly formed in the inner circumferential portion of the retainer plate 7. Therefore, the efficiency of the assembling work of the bearing unit is lowered and the productivity is deteriorated.
In the DE102004031830 described above, it is necessary to provide two plastic working steps, one is a step in which the large diameter hole portion 7a is formed by a press machine in the inner circumferential portion of the end axial portion of the retainer plate 7 and the other is a step in which an end face of the large diameter hole portion 7a is pressed and deformed in the axial direction by a press machine. Therefore, the efficiency of the assembling work of the bearing unit is lowered and the productivity is deteriorated.
Further, in the DE102004031830 described above, it is necessary to individually press a plurality of portions in the circumferential direction of the end face of the large diameter hole portion 7a formed on the retainer plate 7 in the axial direction by a press machine. Therefore, the efficiency of the assembling work of the bearing unit is lowered and the productivity is deteriorated. In this connection, it can be considered to form the engagement pawls 8 by pressing a plurality of portions all at once by using an exclusive press machine. However, in this case, it is necessary to newly prepare the exclusive press machine and further, if dimensions of the bearing are changed, it is impossible for this exclusive press machine to cope with the change in the circumstances.